An assembled battery, which is a rechargeable battery, is used to power a vehicle such as an electric automobile or a hybrid automobile. The assembled battery includes a plurality of battery units connected in series or in parallel. Studies have been conducted on such assembled batteries to develop a technique for dismantling assembled batteries that have been collected to take out battery units and reconstruct (rebuild) assembled batteries using reusable ones of the battery units. However, assembled batteries having a usage history (i.e., used assembled batteries) have different voltages due to overcharging, over-discharging, or memory effect. Further, battery properties such as the battery capacity change in such assembled batteries. Thus, it is suggested that battery units having superior battery properties be selected and combined to rebuild an assembled battery.
To select battery units having superior battery properties, the battery units need to be evaluated. Japanese Laid-Open Patent Publication No. 2011-216328 describes a conventional evaluation method for selecting a battery unit (battery module) that is used for rebuilding when the battery properties of the battery unit such as the open end voltage, the internal resistance, and the remaining charge amount are within an absolute tolerable range, which is set regardless of the assembled battery, and the battery properties are also within a relative tolerable range, which is set for each assembled battery. The relative tolerable range is a range of variations tolerated for each assembled battery and varies in accordance with the assembled battery.